Creators Adam Horowitz and Eddy Kitsis of 'Once Upon a Time' will direct the pilot episode.

Freeform's summer camp horror anthology series is heating up.

Zelda Williams (Teen Wolf), Alberto Frezza (Touch) and Eli Goree (The 100) have joined Dead of Summer, the new drama from the creators of Once Upon a Time, The Hollywood Reporter has learned.

Additionally, creators Adam Horowitz and Eddy Kitsis will direct the first episode of the project, which received a straight-to-series order in November.

Dead of Summer takes place in the late 1980s and follows the counselors at a seemingly idyllic Midwestern summer camp called Camp Clearwater as they experience their first loves, first kisses and first kills. However, Clearwater's dark, ancient mythology awakens and what was supposed to be a summer of fun quickly turns into one of terror at every turn.

Williams will play a counselor at Camp Clearwater, a mysterious loner with no interest in bonding with the rest of the group. The actress is repped by The Gersh Agency and Creative Partners Group.

Frezza has been cast as Deputy Garrett Sykes, a young deputy who has ties to Camp Clearwater and who quickly grows suspicious when events at the camp don’t quite add up. The actor is repped by Innovative Artists and Principato-Young Entertainment.

Goree will portray Joel, an aspiring filmmaker who returns to Camp Clearwater as a counselor and begins to buy into the idea that something weird is happening. The actor is repped by Play Management.